Multiple electrode radiofrequency generator

ABSTRACT

A method and apparatus for application of an electrical signal to neural and other target tissue in the living body can include a device connected to at least two electrodes, wherein temperature sensors are incorporated into tip portions of said electrodes and a a high frequency generator operatively associated with said device.

TECHNICAL FIELD

The invention relates generally to field therapy.

BACKGROUND

The use of radiofrequency (RF) generators and electrodes in neuraltissue for the treatment of pain and functional disorders is well known.Included herein by reference, an as an example, the RFG-3C Plus RFGenerator of Radionics, Inc., Burlington, Mass., and its associatedelectrodes are used in the treatment of the nervous system, and thetreatment pain and functional disorders. This device is capable ofdelivering high frequency energy to patient tissue via an adaptedelectrode, and associated ground or reference electrode. This device isalso capable of delivering low frequency stimulation pulses that areused to accurately localize the electrode placement before treatment.This unit delivers high frequency signal output both in a continuous RFmode and in a pulsatory RF mode, referred to as pulsed RF (PRF). Incontinuous RF mode, target tissue is heated near the uninsulatedelectrode tip of the high frequency electrode by the application of ahigh frequency signal output from the RF generator onto the tissue nearthe uninsulated electrode tip. For example, in continuous RF mode, it iscommon that a target tissue is heated in the range of 45 to 100° C. toselectively destroy the target tissue by heating. In the pulsed RF mode(PRF), intermittent bursts of high frequency signal output are deliveredby the RF generator and applied to target tissue through the uninsulatedelectrode tip of the high frequency electrode. This is typically used totreat pain syndromes. The PRF signal output typically comprises a shortperiod of on-time of high frequency signal, for example 0.1 to 50milliseconds of on-time, followed by a period of off-time which has aduration that is substantially longer than the duration of the on-time(for example, 100 to 1000 milliseconds) in which the signal output issubstantially lower than the signal output in the on-time burst, forexample, near or at 0. The bursts of high frequency signal output aretypically in the range of one to five bursts per second, referred to aspulses per second (pps), or Hertz (Hz). Because in PRF in the on-timeperiod, signal output occurs for a short period, the amount of tissueheating near the uninsulated electrode tip of the high frequencyelectrode is reduced compared to, continuous RF mode for the samemagnitude of signal output.

The RFG-3C Plus generator has one electrode output jack for connectionto a single active electrode, and it has one reference electrode jackfor connection to a reference electrode. When the active electrode isinserted into the body, and the reference electrode is placed, typicallyon the patient's skin, then RF current form the RF generate flowsthrough the patient's body between the two electrodes. The generator canbe activated and its signal output can be applied between theelectrodes. Typically, this is referred to as a monopolar configurationbecause the active electrode is of smaller area than the referenceelectrode, and so the concentration of RF current is highest near it andthe action of the RF electric field, whether for heating or for pulsedRF field therapy is greater there. This usually referred to as a singleelectrode configuration since there is only one “active” electrode.

Parameters that can be measured by the RFG-3C Plus RF generator includeimpedance, HF voltage, HF current, HF power, and electrode tiptemperature. Parameters that may be set by the user include time ofenergy delivery, desired electrode temperature, stimulation frequenciesand durations, and level of stimulation output. In general, electrodetemperature is a parameter that may be controlled by the regulation ofhigh frequency output power. Existing RF generators have interfaces thatallow the selection of one or more of these treatment parameters, aswell as various methods to display the parameters mentioned above.

In another example, the reference electrode can be inserted into thepatient's body, and it can have an active area that is smaller and ofcomparable size to the active electrode. In that case, both electrodesbecome “active” in the sense that both of the have high temperature orelectrical field effects on the tissues around them, so that they areboth involved actively in the therapeutic effects the RF signal output.This can be referenced to as a single “bipolar” configuration.

A limitation for the monopolar and the bipolar configuration justdescribed is that it limits the RF therapy to one or two electrodelocations, respectively. In same situations it is desirable to treatmore than one or two positions in the bodily tissue, and thus desirableto have more electrodes involved as the procedure goes on. For example,this can save time if there are multiple sites to be treated, as forexample, multiple levels of the spinal medial branches to be treated forback pain.

The Untied Stated Patent Application Publication entitled Method andApparatus for Diagnosing and Treating Neural Dysfunction, by W. J.Rittman, Pub. No. US 2007/0032835 A1, Pub. Date: Feb. 8, 2007, describesan RF generator system comprising an RF generator with multiple activeelectrode output connections that enables the RF signal output thegenerator to be connected and delivered simultaneously to more than oneelectrode to deliver a therapeutic effect at each of the electrodepositions at the same time. The RF generator's signal output is switchedby switches and switch controllers so that the RF generator's output isapplied to multiple electrodes at the same time, that is,simultaneously. In another aspect, the RF generator's switches andswitch controllers are independent, that is the switch and switchcontroller for one of the electrodes performs independently from thoseof a second electrode or from those of multiple individual electrodes.This has one disadvantage that, because the signal output can be appliedto more than one electrode at the same time, the voltage of thegenerator's power supply and output electronics can be loaded down atthe same time, causing sag or droop of the signal output voltage duringapplication. Another disadvantage is that the electrical field from eachof the electrodes adds coherently in the bodily tissue, making it moredifficult to separate their individual effects on the bodily tissue.Another disadvantage is that it makes it more difficult to control theRF signal output and to maintain the RF signal output so as to maintainthe temperatures of the electrodes at a set temperature chosen by theuser.

Examples of high frequency generators and electrodes are given in thepapers of entitled “Theoretical Aspects of Radiofrequency Lesions andthe Dorsal Root Entry Zone,” by Cosman, E. R., et al., Neurosurgery15:945-950, 1984; and “Methods of Making Nervous System Lesions,” byCosman, E. R. and Cosman, B. J. in Wilkins R. H., Rengachary S. S.(eds): Neurosurgery, New York, McGraw-Hill, Vol. III, pp. 2490-2498,1984, and are hereby incorporated by reference herein in their entirety.

Four patents have issued on PRF by Sluijter M. E., Rittman W. J., andCosman E. R. They are “Method and Apparatus for Altering Neural TissueFunction,” U.S. Pat. No. 5,983,141, issued Nov. 9, 1999; “Method andSystem for Neural Tissue Modification,” U.S. Pat. No. 6,161,048, issuedDec. 12, 2000; “Modulated High Frequency Tissue Modification,” U.S. Pat.No. 6,246,912 B1, issued Jun. 12, 2001; and “Method and Apparatus forAltering Neural Tissue Function,” U.S. Pat. No. 6,259,952 B1, issuedJul. 10, 2001. These four patents are hereby incorporated by referenceherein in their entirety.

In one example of the use of RF generators, a patient may complain ofback pain, or some other pain of known or neuropathic origin. Aclinician will often perform diagnostic blocks with local anesthetic byinjecting the anesthetic into the areas that are suspected of generatingthe pain. If the patient receives temporary pain relief from theseinjections, the doctor concludes that the anatomical positions of theorigin sites of the pain are in the locations where he made theseinjections. Unfortunately, the origin of pain is poorly understood;perceived pain at a certain level in the back, for instance, canactually be created from many different and multiple sources andanatomical locations.

Once a location has been identified, the clinician will decide todeliver high frequency signal output form a high frequency generator tothis location to permanently destroy the source of the pain. A ground orreference plate will be placed on the patient's thigh to provide areturn path for the high frequency energy. An insulated electrode with asmall uninsulated tip will be placed at the expected target location.Stimulation pulses will be delivered at a sensory frequency (typically50 Hz), and a stimulation voltage signal output will be applied to theelectrode. The clinician is looking for a very low threshold of responsefrom the patient (e.g., less than 0.5 V) to ensure that the electrode isclose to the sensory nerves. They will then perform a stimulation testat a muscle motor frequency (e.g., 2 Hz), and increase the stimulationvoltage output to 2 volts. In this instance, they are looking for nomotor response in the patient's extremities as this would indicate theelectrode was too close to the motor nerves. Treatment in this areacould cause paralysis. Upon successful completion of these tests, highfrequency energy is typically delivered for one or more minutes, whilemaintaining an electrode tip temperature between 70 and 90 degrees.Alternatively, high frequency signal output can be delivered for one ormore minutes, but in a pulsed mode where the high frequency signaloutput is on for a short period of on-time and off for a long period ofoff-time, and thus the pulsed high frequency application will notproduce any appreciable heating (reference is made to sited patents inthe Background section herein)

Although these treatments are successful, they have several drawbacks.In practice, most patients need treatments at several different nervelocations. This requires placing the electrode, performing thestimulation, and delivering the high frequency signal output at eachlocation, and then repeating the process. This can cause a great deal ofwasted time, and patient discomfort, while waiting for the highfrequency signal output to be delivered. Another drawback is that, inspite of successful stimulation testing; the target nerve is often notdestroyed, thus resulting in no decrease of pain. The clinician is leftto determine whether the target nerve has been missed, or whether thepain generator is located elsewhere in the body.

SUMMARY

The present invention relates generally to the applications of RF tomultiple electrodes positioned in tissue of the living body. In oneexample, an RF generator has connections to more that one electrode sothat therapeutic effects can be delivered to multiple sites on theliving body during the same treatment session. An RF power source in theRF generator connects to the individual electrodes through switches andcontrollers in a way that the signal output of the RF generate isdelivered non-simultaneously to the electrodes. In one example, theswitches and the controllers for the individual electrodes are dependenton each other to assure, for example, that the signal output of thepower source is only connected to one electrode at a time. In anotherexample, the controllers and switches are made dependent so that thesignal output of the generator is only connected to bipolar pairs of themultiple electrodes at separate times, that is, non-simultaneously. Oneadvantage of this non-simultaneous connection to the individualelectrodes is that the signal output, for example, the voltage of thepower source, is only being delivered to one electrode at a time, andthus the power source will not be over-loaded and thus its signal outputwill not be pulled down or sag. Another advantage is that, in oneexample, since only one electrode is activated at a time, thetherapeutic agent, for example, heat or the electrical field is appliedto the target tissue separately in time slices. This has an advantagethat that the circuit controls for each electrode can be operatedseparately in time from the circuit controllers of the other electrodes.This has one advantage of simplifying the control algorithm for overallcontrol of the heating and overall time of the treatment of theprocedure. The generator can deliver programmatically the high frequencysignal output to each of said electrodes and/or the generator candeliver sequentially the high frequency signal output to each of saidelectrodes.

In one example, the signal output of the RF generate is appliednon-simultaneously in a cyclical time sequence that is controlled by amaster timing controller in the RF generator. One advantage of that isthe signal is applied in a smooth time sequence. The time space can bedivided into time bins or time slices, each time slice being devoted toone electrode, and the time slices repeat themselves in cyclical manner.The electrode controllers synchronize the series of these time slicesand thus synchronize the delivery of the high frequency signal outputapplication to the multiple electrodes. One advantage of this is thatthe control algorithm is separable in terms of the temperature and thetime bin slice for an individual electrode, making the entire control ofthe multi-electrode application linear and separable in time.

In one example, the dependent controllers are synchronized with a commonclock. During the on-time time slice for an individual electrode, itscontroller will apply an amount of signal output, for example, voltage,on that electrode with sufficient amplitude, has governed by thecontroller, to elevate the temperature or the electrical field at thatelectrode. In one example, the controller can be connected to atemperature sensor in the electrode so that the signal output leveldelivered to the electrode as governed by the controller, is determinedby comparison of the measured temperature at the temperature sensor to aset temperature decided upon or, in one example, by the operator. Inanother example, during the time slice of one electrode, the signaloutput level applied to the electrode can be delivered to the electrodefor a variable fractional time during the time slice, so that thecontroller can drive, for example, the temperature or the electric fieldat the electrode towards or away from some target or set value or, inanother example, towards a set value that has been pre-set by the useror which is derived by a feed-back algorithm programmed into thecontroller.

In another example, the time slices relate to individual pairs ofelectrodes that are to be used in a bipolar configuration. Bipolar pairsare activated during non-simultaneous times and by dependent,coordinated controllers. One advantage of this is that bipolar pairs ofelectrode can be activated separately and without coherent interferencefrom another pair of bipolar electrode pairs.

Disadvantages of the prior art are overcome by the present method andsystem which relate to delivering the signal output from a highfrequency generator non-simultaneously to more than one treatmentelectrode that are involved in the clinical procedure. In one example,the high frequency signal output is cyclically sequenced to the multipleelectrodes so that no two electrodes have the high frequency signaloutput applied to them at the same time, and the signal outputs to eachelectrode are regulated by a feedback mechanism included in the systemsuch that each electrode's tip temperature is maintained to a level (settemperature) set by the user. This greatly reduces treatment time,providing the patient with a shorter period of discomfort as well as notwasting valuable clinician and procedure-room time.

In one example, EMG measurements are displayed on the system to allowthe clinician to determine whether the target nerve has been destroyed,as well as the display of pre-treatment and post-treatment sensorystimulation thresholds to measure the degree of desensitization of thetarget nerve. Measuring the EMG signals allows the clinician todetermine whether the target nerve has been successfully treated.Comparison of pre-treatment and post-treatment sensory stimulationthresholds gives the clinician an immediate look at the desensitizationof the target nerve.

In one example, the system can deliver at different times in theprocedure, both high frequency signal output as well as low frequencystimulation pulses. The device can be, in turn, connected to greaterthan one treatment electrode. These electrodes have temperature sensorsattached to their tips, which reports the tip temperature of eachelectrode to the system. The system has a user interface which allowsthe signal output from the system, in one mode, to be connectedindependently and/or individually to each of the multiple electrodes,and also, in another mode, to enable the high frequency signal outputfrom the system to be connected in sequenced, non-simultaneoustime-cycles to the multiple electrodes that are connected by cables tothe system. In this way, the low-frequency stimulation signal outputfrom the system can, in one phase of the procedure, be independentlyconnected to each of the patient electrodes. Then, in another phase ofthe procedure, the high frequency signal output from the system can beconnected non-simultaneously, and in a sequential manner that iscontrolled by the system, to the multiple electrodes. Temperatureregulation of the temperature measured at the multiple electrodes can becontrolled by the system during the time that the high frequency signaloutput is being applied in the heating phase of the procedure. Thesystem can provide the capability of both sensory and motor stimulationtesting, as well as impedance monitoring to be performed on each of themultiple electrodes during the procedure. When it is desired that thetherapeutic high frequency signal output is to be delivered, the userinterface allows the non-simultaneous, sequential connection themultiple electrodes to be carried out by the system control electronicsand feedback algorithms. Tip temperatures from each of the multipleelectrodes can be readout and stored in the system, and a settemperature for each electrode can be chosen by the user. The device cancontinually compare each of the temperatures from the electrodes to theset temperature. If the electrode tip temperature for an individualelectrode exceeds the set temperature, the high frequency signal outputto that electrode can be reduced during the programmed time slice ofactivation of the high frequency signal output to that electrodeSimilarly, if the electrode tip temperature is less than the settemperature, the high frequency signal output to that electrode can beincreased by the system control electronics.

In one example, a system graphic display, which allows EMG and/or EEGsignals to be recorded and displayed. In another example, speaker and/ora headphone output allow the EMG and/or EEG signals to be audiblydetected and analyzed.

In one example, the present system and method can comprise a highfrequency power source that is integrally built into the system. Inanother example, the system can comprise a stand-alone peripheral devicethat can be connected between a high frequency power source and themultiple electrodes.

In one example, the system and method of the present invention can beapplied to the nervous system for the treatment of pain and/orfunctional neurological diseases such as Parkinson's disease or mooddisorders. In another example, the system and method can be applied totreat cancerous tumors or other functional disorders anywhere in thepatient's body.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the Claims.

DESCRIPTION OF DRAWINGS

In the drawings that constitute part of the specification, embodimentsexhibiting various forms and features hereof are set forth,specifically:

FIG. 1 is a schematic diagram showing a high frequency generator withfour electrodes connected to it and a graphic display.

FIG. 2 is a schematic diagram showing feedback and control circuitry.

FIG. 3 is a schematic diagram showing a circuit block elements fordependent control of three electrodes connection to a high frequencygenerator with non-simultaneous energizing of the electrodes.

FIG. 4 shows a schematic diagram of time slices with non-simultaneoussequencing of electrode activation with respect to a high frequencygenerator.

FIG. 5 shows a schematic diagram of cyclical sequencing of time slicesof electrode energizing with signal output amplitude variations toenable feedback control of the high frequency therapy.

FIG. 6 shows a schematic diagram of time-bin slices that are cyclicallysequenced so that the multiple electrodes are energized separately intime, and the magnitude of the heating effect for a given electrode ismodulated by varying the percent of on-time of the signal output duringthe time-bin slice for that electrode.

FIG. 7 shows a schematic block diagram of an electrical circuitcomprising a master timing and coordinating controller that the controlsthe individual feed-back controllers of the individual electrodes.

FIG. 8 shows a schematic diagram of a multi-electrode high frequencyelectrode system comprising multiple pairs of bipolar electrodes.

FIG. 9 is a schematic diagram showing a high frequency generator withfour electrodes connected to it and graphic display.

FIG. 10 is a schematic diagram showing a high frequency generator withEMG graphic display and multi electrode connections.

FIG. 11 is a schematic diagram showing a high frequency generator withfour electrodes connections, graphic display, and recording ofstimulation testing thresholds.

FIG. 12 is a schematic diagram showing a high frequency generate withmulti-electrode connections, graphic display, and flexible modeselection buttons.

FIG. 13 is a schematic diagram showing a block diagram of circuitelements for cyclical non-simultaneous sequencing to a four electrodes.

FIG. 14 is a schematic flow diagram for non-simultaneous sequencing ofgenerator output to multiple electrodes.

DETAILED DESCRIPTION

Referring to FIG. 1, an RF generator 1 that can be connected to multipleelectrodes is shown. Signal output from the generator can connect tooutput jacks 4, 7, 11, and 14. Electrodes 44, 47, 52, and 54 can beconnected to the output jacks by cables 24, 27, 31, and 34,respectively. Mode select switch 3 allows the user to switch between anindividual output mode of the generator 1 wherein signal output from thegenerator 1 is connected to individual electrodes, one at a time, or toa multiple output mode wherein signal output from the generator 1 isconnected in a cyclical, non-simultaneous sequence to multipleelectrodes 44, 47, 51, and 54. The individual mode permits the RFgenerator signal outputs to selectively be connected to each electrodeindividually for the purpose of doing individual impedance measurements,stimulation threshold testing, EEG or EMG recording, or individualelectrode RF lesion making. The multiple out mode of the mode selectswitch allows therapeutic high frequency signal output from thegenerator 1 to be delivered to the electrodes 44, 47, 51, and 54 in acyclical sequence that is automatically programmed into the generator 1,so that the high frequency energy is delivered in a sequential andnon-simultaneously time pattern to the multiple electrodes.

The individual electrode temperatures can be measured either in asequential or in a continuously time pattern and the measuredtemperatures can be compared to the user set temperature, represented bythe display 77 and set by the knob 55 in FIG. 1. For example, in thisembodiment the individual electrode temperatures are displayed on atwo-dimensional graphics panel identified by 60 in the figure. Alsowithin the graphics display is a representation of temperature versustime displayed in graphic format, for example, as line graphs 61, 62,63, and 64 in FIG. 1. Indicator lights, represented, for example, by 65in FIG. 1, indicates which electrode or which set of electrodes arebeing used in the procedure. In this way the user always knows whichelectrode is intended to be active or is activated when the mode select2 has been set to a particular electrode or set of electrodes, and willalso indicate during high frequency therapeutic treatment whichelectrodes are being involved in the procedure according to the systemand method described herein.

Referring to FIG. 1, in one example, the high frequency power source orhigh frequency generator that delivers the high frequency signal outputand/or low frequency stimulation signal output pulses could beincorporated into the apparatus 1, or could be a separate stand-aloneunit, with the apparatus 1 being interposed between the high frequencypower source and the electrodes. In one example, as illustrated in FIG.1, an AC line 68 can connect the apparatus 1 to an electrical outletsupply power for the apparatus 1. In another example, apparatus 1 can bea battery-operated device wherein the power is supplied by a battery(not shown) that can make the apparatus 1 portable.

The mode selection 2 can be implemented in many ways, for example,knobs, pushbuttons, remote control voice control, or other means. In oneexample, the features of the user interface of apparatus 1 could beachieved with or without displays such as 60, and, in one example, canuse up/down pushbuttons rather than rotatable selector knobs to selector advance or decrease control levels. In one example, the mode select 2can connect each electrode individually to the high frequency powersource, and can also have another position which connects each electrodeindependently to an EMG or EEG measuring circuit, where the EMG or EEGsignal can be displayed on a two-dimensional graphics display. In oneexample, an additional position on the mode select 2 can deliver highfrequency signal output comprising either, (a) in one mode, continuoustrains of high frequency signal waves, or (b) in another mode, trains ofpulsed high frequency signal bursts. In one mode, for example, thesemodes of high frequency signal output can be delivered by a programmedcyclical sequence non-simultaneously to multiple electrodes that havebeen selected by the user to be active during the procedure. In oneexample, a feedback circuit can be incorporated into apparatus 1 whichis adapted to maintain each electrode tip at a temperature equal to aset temperature, for example, a value set by the by control 55 anddisplayed, as for example, by the digital display 77.

In other possible ergonomic embodiments of this invention, additionaldisplays, buttons, and/or indicators can be included to allow and/orassist the operator in controlling the device. For example, in FIG. 1 anRF ‘ON’ indicator light, represented by 69, can indicate when highfrequency signal output is being delivered to electrode outputs.

Referring to FIG. 2, in one example, a logic control diagram shows abasic feedback mechanism for each of the temperature controlledelectrodes that are connected to the apparatus such as 1 in FIG. 1. Highfrequency power supply 95 delivers high frequency signal output. Thetemperature of the electrode receiving this high frequency signaloutput, as measured by a temperature sensor in the electrode, and theuser selected set temperature, are delivered to a logic circuitdecision-making element, and represented by 97. If the electrodetemperature is greater than the user set temperature, the high frequencypower or signal output to that electrode is reduced or turned off. Thisaction is represented by block 98. Then this process starts all overagain, where the electrode temperature is once again compared to theuser set temperature. Conversely, if the measured temperature for thatparticular electrode is less than the user set temperature the highfrequency signal output remains on or increased, and the electrodetemperature is subsequently compared to the user set temperature. Inthis way temperature feedback is realized, which will maintain theelectrode temperature at the same level as the user set temperature.

Referring to FIG. 3, a schematic diagram is shown, in one example, of afeedback and control system involving the use of multiple high frequencyelectrodes. The system is configured and controlled so that theelectrodes 145, 146 147. The electrodes are connected to the system, andthey are in contact to the patient's body B. The electrodes receive thesignal output from the high frequency generator supply 100 in anon-simultaneous sequence, so that an individual electrode receivespower from the high frequency power source during a time slice duringwhich the other electrodes do not receive the high frequency power. Forexample, in FIG. 3, there are three electrodes 145, 146, and 147 thathave cable connections 142, 142, and 143, respectively, to the system.These connections connect to switches S1, S2, and S3, respectively, thatconnect further through connections 101, 102, and 103, respectively, tothe high frequency generator 100 that supplies the high frequency signaloutput that energizes the electrodes. In one example, as illustrated inFIG. 3, the switch S1 is closed in the time slice corresponding to thestate of the system shown in FIG. 3, and at this same time slice theswitches S2 and S3 are both open. Thus in the time slice of FIG. 3, onlythe electrode 145 can be activated or connected to the signal output ofthe high frequency generator 100. This condition that S1 is closed iscontrolled by the controller 131. Controller 131 is connected logicallyto controller 132 and to controller 133, that control the stateelectrode of switches S2 and S3, respectively, by the connections 170and 174. In one example, the controllers 131, 132, and 133 are logicallylinked so that only one of the switches S1, S2, or S3 can be closed atany given time. This means that the electrodes cannot be energized bythe signal output of the high frequency generate 100 at the same time;that is they are energized non-simultaneously. For example, at anothertime, S2 can be closed, and S1 and S3 must be open. At another time, S3is closed, and S1 and S2 must be open. In one example, the controllers131, 132, and 133 can be cyclically synchronized by a common clocksignal so that they close and open the switches automatically in timeslices that repeat according to programmed cycle built into thecontrollers. The common clock or the common synchronizer can be aseparate element (not shown) or can be clocks built into one or more ofthe controllers 131, 132, or 133. In one example, the controllers 131,132, and 133 are cyclically activated so that the electrodes areallotted specific repeatedly cycled time slices in which they areconnected non-simultaneous to the high frequency generator. During anelectrode's allotted time slice, for example, for electrode 1, thecontroller for that electrode, for example, controller 131 for electrode145, will controller the amplitude or the dwell time of the signaloutput from 100 so that the power on electrode 145 will be such as todrive the temperature, measured by the temperature sensor 161, towardthe set temperature for electrode 145 as set on 121. This is a feedbackcontrol on temperature for electrode 1 that can be carried out by thecontroller 131.

Referring to FIG. 3, each of the electrodes has a temperature sensorbuilt into them indicates by the elements 161, 162, land 163,corresponds to electrodes 145, 146, and 147, respectively. For example,the temperature sensors can be TC thermocouple sensors that are commonlyused in RF electrodes. The temperature signal can be fed into thecontrollers by the connections 151, 152, land 153, respectively. In oneexample, there can be a set temperature control, illustrated by theelements 121, 122, and 123, whereby the user can set a temperature whichthe respective electrodes should lock onto during the procedure. As anillustration of how the circuit can function, electrode 1 can be chosen,as an example, during the time slot for which it is energized. The samedescriptions can apply to electrode 2 and electrode 3 during theirrespective time cycles. Temperature sensor 161 is incorporated intoelectrode 145 that reports the temperature at the tip electrode 145. Thehigh frequency power connection 141 connects to the electrode 1 that inturn connects to the tissue around electrode 145 in the patient's bodyB. The high frequency power thus passing into the tissue heats thetissue, and, in turn, heats up the electrode 1 and the temperaturesensor 161 within it. Temperature measured by 161 is reported via 151 tocontroller 131. Control 131 also has an input signal from settemperature control 121, and compares the set temperature to themeasured temperature from 161 to determine how long switch S1 should beclosed and when it should be opened during the allotted time slice forelectrode 145. In this way, the electrode temperature can converge tothe set temperature. Switch S1 is shown as a generic switch, and cancomprise electrical, mechanically and/or optically switching technology.The high frequency power source 100 is connected and disconnected toelectrode 145 via switch S1 and the opening and closing of S1 ismodulated, in one example, via controller 131. Controller 131 comparesthe user set temperature from 121 to the reported electrode tiptemperature from sensor 161 and determines the delivery of the signaloutput from supply 100 to electrode 145. This is an example of afeedback circuit is established to maintain the temperature of electrode145 at the user set temperature. A similar feedback control forelectrodes 2146 and 147 can be done during heir respective on-timeslots. In this way, the electrodes can be energized by the highfrequency power source in a non-simultaneous manner, and the temperatureon the multiple electrodes can be controller according to chosen settemperatures in a relatively continuous manner during the clinicalprocedure. The procedure carried out by the illustrative circuit of FIG.3 can be done for other numbers of high frequency electrode, forexample, two, or four, or any number of electrodes.

Referring to FIG. 4, a sequence of time slices T1, T2, T3, T4, . . . etcare indicated on the vertical axis, and the state of the switches, asfor example, the switches S1, S2, and S3 in FIG. 3, are shownschematically in configuration of open and closed states. For example,in time slice T1, switch S1 is shown in a horizontal position 200,meaning that it is closed, and switches S2 and S3 are shown in an openstate indicated by the inclined angle of the schematic switch arms 202and 204, respectively. This would be the condition in which the signaloutput from the high frequency generator is delivered to electrodeassociated with S1, as for example, the electrode 145 in FIG. 3. Thisstate can be controlled by the controllers, for example, shown in FIG.3. In the next time slice T2, S1 is open indicated by 207, S2 is closeindicated by 209, and S3 is open indicated by 211. This corresponds tothe signal output being delivered the electrode 146 in FIG. 3, but inthat time slice T2, no signal output is being connected to theelectrodes 145 and 147. In the next time slice, T3, S3 is closedindicated by 214, and switches S1 and S2 are open indicated by 218 and219, respectively, so that the electrode 147 in FIG. 3 is activated, andthe other electrodes 145 and 146 are not. This cycle of switches beingopened and closed in successive time slices continues as shown in FIG.4. In one example, the length of time of the time slices can becontrolled by the controllers as for example, 131, 132, and 133 in FIG.3. The dwell time of signal output on a particular electrode in aparticular time slice can be modulated by the controllers according tothe measured temperature of the electrodes and the feedback controlcircuit as describes with respect to the FIGS. 1, 2, and 3.

Referring to FIG. 5, in one example, the signal output level V of thehigh frequency generator is displayed schematically on the verticalaxis, and the time slices T1, T2, T3, etc are shown schematically on thehorizontal axis. As in the previous figures, the time slices cancorrespond to the non-simultaneous time slots for the opening of theelectrodes. In one example, the time slots can be of equal duration. Forexample, if the time to cycle through all of the electrodes is onesecond, then the individual time slices for each electrode can have⅓-second durations. The time slices T1, T4, T7, etc can corresponds tosignal output connection to electrode 145 of FIG. 1; T2, T5, T8, etc cancorresponds to electrode 146; and T3, T6, T9, etc can corresponds toelectrode 147. During each time slice, the controllers, as for example131, 132, and 133 in FIG. 3, can deliver the appropriate level of signaloutput V to the corresponding electrode, whereby, for example, thetemperature of the electrode can be chosen at the set temperature. Inone example, the level of electrode 146 corresponding to T2 is held atthe value V2, then at slice T5 it is held at V5, and at T8 at level V8,and so on, these values being chosen or governed by the controller ofthe electrode 146 so that the temperature measured at the electrode canbe held at a desired level. The same electrode prescription can applyfor the other electrodes and their times slice. One advantage is thatbecause the time slices and the signal output are non-simultaneouslyapplied, the controllers that are synchronized to discriminate the timeslices can individually feedback control each electrode separatelyduring their respective time slices. Another advantage is that since thesignal output is non-simultaneously applied, the high frequency powersupply is not loaded down during each time slice with more than oneelectrode, so that it can better maintain it source signal outputlevels.

Referring to FIG. 6, another example of a feedback control method isillustrated schematically. The cyclical time slices for the electrodesis shown on the horizontal axis, and the signal output level on thevertical axis as in the FIG. 5. In this example, during a given timeslice sequence such as, for example, the group of slices T1, T2, and T3,the level is held by the dependent controllers for the electrodes atVV1. During time slice T1, the duty time of the output can be controlledby the controller to be a fraction of the slice time T1, as illustratedby the time D1. Time duration D1 is controlled so that the temperatureof the electrode 145 is steered back, by a feedback algorithm in thecontroller for electrode 145, to the set temperature value. Similarly,in the next group of time cycles are T4, T5, and T6. During the timeslice T4 in which the electrode 145 is active, the dwell time of thesignal output to the electrode 145 is D4. In T7, it is D7, and so on.The level at each group of time cycles can be changed as illustrated inFIG. 6 by the levels VV1, VV2, VV3, and so on. The level that ismaintained and applied at each group of time cycles, can be determinedby the feedback algorithm so that each and all of the electrodes can getthe sufficient power of signal output during its allotted time slice toachieve the temperature of the set temperature. This can be done by thedependent coupling of the controllers, as, for example, indicate by thecoupling lines 170 and 174 shown in FIG. 3.

Referring to FIG. 7, a schematic block diagram of circuit elements areshown that can dependently couple the controls for multiple electrodesE1, E2, E3 that can be connected to a high frequency generator 250. Highfrequency generator 250 is connected by connection 251 to a mastercontroller 254, which controls the distribution of the signal output of250 to the secondary controllers 271, 272, and 273. The secondarycontrollers, in turn, send the activation signal to the electrodes E1,E2, and E3, respectively. In one example, controller 254 comprises amaster clock that determines the group cycle times, the time sliceswithin the group cycle times, the signal output levels during each timeslice, and/or the dwell times within each time slice corresponding tothe electrode activations by the signal output from 250. This mastercontrol information is sent to the controllers 271, 272, and 273 by theconnections 261, 262, and 263. In one example, the temperature signalsfrom the electrode temperature sensors within the electrodes E1, E2, E3are inputted, as illustrated by T11, T22, and T33, into set temperaturecontrollers 281 282, and 283, respectively, which then send theirsignals to the controllers 271, 272, and 273, respectively, forsecondary control of signal output levels and/or dwell times during eachelectrode time slice. This can enable the controllers to maintain adesired set temperature for each electrode. Also, in one example, theconnections 261, 262, and 263 can comprise transport of an informationsignal back to the master controller 254 (indicated by the two-way arrowheads on these connections), based on the measured temperature, the settemperature, and the time slice parameters, so that master controller254 can set the overall signal output level from the high frequencysupply 250. This flow of information and control from 254 to 250 isschematically illustrated by the two-way arrow heads on the connection251.

Referring to FIG. 7, a connection 300 is shown to a reference electrode304. Reference electrode 304 can for example, be a grounding plate orpad that is connection to the patient's body skin to act as a returncurrent path for the output of the high frequency generator. This is acommon type of connection. In another example, the electrode E1, E2, E3,and more if the clinical need warrants it, can include referenceelectrode such as electrode 304, so that the system is then connected inmultiple bipolar manner. The reference electrode can be of the same typeas high frequency element normally inserted into the patient's body forRF lesioning, so that the reference electrode themselves become part ofthe therapeutic system, rather than being merely a passive return pathfor high frequency current.

Referring to FIG. 8, a system of multiple electrodes connected to a highfrequency generator is shown wherein the electrodes are configured in amultiple bipolar manner. In one example, the multi-bipolar signaloutputs from generator 400 are sent out of jacks 460 and 462, each jackhaving multiple pin outputs that can send non-simultaneously cyclicalsignal outputs to multiple pin combinations. The cables 411 and 412carry these signal outputs through multiple internal cables (not shownin the figure), and have a multiplicity of continuation cables, such as441, 443, 445, 447, and 449 from line 411; and 442, 444, 446, 448, and445 from line 412. These continuation cables, in turn, connect to theelectrodes EE1, EE3, EE5, EE7, and EE9 for the continuation linesfanning from 411, respectively; and electrodes EE2, EE4, EE6, EE8 andEE10 from the continuation lines sited from cable 412, respectively. Inone example, the pairs of bipolar electrodes, for example, EE1 and EE2are activated as a bipolar pair, and the high frequency generator withits internal, non-simultaneous control functions, as described inconnection with the previous figures, can activate these bipolar pairsto hold a desired set temperatures on them or to maintain them at aspecific signal output level. Another time slice would apply to thebipolar pair EE2 and EE3 with their respective time slice andnon-simultaneous activation and controls, and so on for all the bipolarpairs involved.

Referring to FIG. 8, in another example, the output lines 411 and 412from the high frequency generate 400 can each carry a single highfrequency bipolar signal that is connected directly though theconnection lines 441 443, 445, 447, and 449 for connection 411; and 442,444, 446, 448, and 450 through the connection 412, respectively. In oneexample, the opposite polarity of the high frequency signal output fromgenerator 400 would be connected to each of the respective pairs in thebipolar collection. For example, EE1, EE3, EE5, EE7 and EE9 would carrythe plus signal output level, and EE2, EE4, EE6, EE8, EE10 would allcarry the minus signal output value level. Thus the cabling connectionstructure comprising 411, 412 in combination with 441 through 450 can bea unitized cable system for delivering bipolar signal outputs tomultiple electrodes in a bipolar RF system. This can have applicationwhen delivering, for example, pulsed RF signals to multiple bipolarelectrode pairs.

Referring to FIG. 9, in one example, an embodiment of the user interfaceis illustrated. Displays 500 are digital indicators of electrodetemperatures and/or other pertinent parameters or readouts associatedwith the multiple electrodes that can be connected to the system. In oneexample, they can be displayed in separate displays, and in anotherexample, they can be displayed as part of a two dimensional screendisplay, and the design choice can be dependent on clinical or ergonomicneeds. Digital displays of such parameters or readouts can, for example,be represented by LED or LCD digits. Element 507 represents atwo-dimensional graphics display, and in FIG. 9 is displaying a graph oftemperature from electrode measurements. The dashed curve 509 canrepresent the time course of another parameter, for example, voltage,current, and/or power delivered on-time the electrode(s). The panel 514can be the automatic temperature control panel. The set temperature canbe actuated up and down by the toggle switch, and the set temperaturecan be displayed digitally as, for example, 80. The displays or selectorcontrols, indicated by the element 511, can be lights that indicatewhich of the multiple electrodes that the clinician wished to the activein the procedure, or they can be buttons that enable the clinician toselect which of the multiple electrodes he wishes to be activated duringthe procedure. The present system and method is not restricted tographics display, but can comprising other readout or display method andsystems, including printout and hard copy devices. For example, otheroptions for user interface can comprise the mode selector that can berepresented by a series of buttons that are associated with indicatorlights identified as 511. The electrode outputs are schematically shownas elements 517 which, for example, can be electrode jacks. The elements517 can be the output jacks that enable connection to cable s that runto the electrodes.

Referring to FIG. 10, in one example, the system is shown wherein themode selector 600 has a position for EMG or EEG recording in addition toa stimulation position and a high frequency signal output deliveryposition. On the two-dimensional display 602, an EMG or EEG signal 604can be represented as a graph 604 of EMG or EEG activity or of EMG/EEGactivation signals, thus identifying electrophysiological activity of anerve before and/or after the high frequency treatment. In one example,the elements 612 indicate the electrode output jacks. In the exampleshown, there are four electrode output jacks; however any number ofelectrodes greater than one is included within the scope of the presentsystem and method. In one example, the Set Temp user interface cancomprise a knob 614, however there are other implementations of thiscontrol that are possible, such as up/down switches, slide controls, andso on. Element 620 indicates the set temperature. Displays 624 canindicate the temperature readout values from the electrodes' temperaturesensors, and in the FIG. 10, for example, they are all showing readingbody temperature of 37 degrees which is typically the case before highfrequency signal output is applied to the electrodes.

Referring to FIG. 11, a schematic representation of the system is shown.The mode selector 637 is in the stimulation position. A sensorystimulation graph 630 is displayed. In one example, the graphs for thestimulation levels can be shown for four electrodes. Typically, thestimulation signal output level, for example, voltage, is applied toeach electrode independently and individually, so that the correctposition of the electrode tip can be confirmed on the correct nerve.Each electrode that is connected to the system and is to be activatedhas associated with it a histogram such as 632 indicating, for example,stimulation sensory thresholds prior to making a heat or a pulsed highfrequency lesion. This can be done for each electrode separately. Thereare many possible ways that these stimulation parameters can berepresented. For example, FIG. 11 illustrates one example of the manysuch ways in which to achieve a representation of these stimulationparameters identifiable to the user. The small line 633 can indicate alevel that the clinician has selected for that electrode position andcan show for later record what was achieved. After the heat highfrequency lesion, another stimulation testing can be done for the sameelectrode, and this can be shown as another histogram bar graph, forexample line 634 together with a record index level marker 635. Similarbar graphs can be developed and displayed for the other electrodes, asis illustrated in the FIG. 11. The mode select switch, identified as637, has settings for both delivery of high frequency signal output andfor stimulation signal output. The displays 624 represent thetemperature readouts measured at the electrodes. Typically, whenstimulation is being delivered to the electrodes, there is no highfrequency heating of the electrodes, so that the temperature readings624 for the multiple electrodes would indicate body temperature of 37degrees. The electrode outputs, represented by 612, can indicateconnections to four electrodes, although any number of electrodesgreater than one is anticipated in this present system and method. Settemperature can be adjusted by knob 640, and an example of a settemperature displayed value is represented by display 642.

Referring to FIG. 12, in one example, another user interface is shown. Amode select button, 700, can allow the user to select between EMG/EEG,HF, and stimulate modes. In one example, the modes of: stimulation 750,high frequency output modes 754, recording LOG 758, RAMP of the highfrequency output increase 760, EEG or EMG recording 766, and recordingof the parameters used 768, are actuated by push buttons. When thestimulation or the EMG mode is selected, digital display(s) orpushbuttons The electrode mode or configurations used can be representedby other pushbuttons, for example, 723, which can indicate whichelectrode is selected. Integral he electrode modes, the user can selectone electrode at time for EMG/EEG or stimulation activation. The systemenables the user to know which of the multiple possible electrodes thatare being considered is being connected at any given time to the EMG/EEGor to the stimulation output mode, on-time for the high frequencytreatment. The electrode selection can be made by the knob or pushbuttonas illustrated by element 723. In one example, the user set temperatureis identified as a knob indicated by 720, and the set temperature valueis represented by 722, and this display, in one example, is incorporatedwithin a two-dimensional graphics display 726. A time versus temperaturegraph is indicated by 730 for the individual electrodes, if highfrequency signal output mode is selected on the mode select, isindicated by 754. Display 740, in the example, is in FIG. 12, indicativeof four electrode outputs. Dotted circles 741 represent that more thanfour electrodes or less than four electrodes can be used, according toclinical needs.

Referring to FIG. 13, a schematic diagram of the sequential flow of highfrequency signal output to four electrodes is shown. The signal outputfrom high frequency generator 800 is distributed in a timing cyclethrough the control element 805 which distributes the signal output asindicated schematically by the rotary arrow 807. 807 is symbolically a‘phasor’ showing that the output can first be connected to electrode E1,as shown by the solid arrow 807, and then as time progresses, it isconnected to E2, indicated by the dashed arrow 814. The rotordistributor or ‘phasor’ 807 continues in a schematically indicateddashed clockwise circle 817 representative of the passage of time, sothat it connects in turn with E3 indicated by dashed arrow 820, and E4indicated by arrow 827, and continues on around the cycle to repeat itsconnection automatically to the four electrodes again and again duringthe procedure duration. This can be referred to as ‘cyclodromic’distribution control of the high frequency signal output to multipleelectrodes. The contact to any electrode is non-simultaneous to thecontact with any other electrode, so the process can be said to benon-simultaneously cyclodromic.

Referring to FIG. 14, a flow diagram shows schematically a process forthe method of the present invention, Step 900 comprises the selection ofmultiple electrodes to be used according to clinical needs. Step 900 caninclude the decision on how many electrodes are needed to fulfillclinical objectives the procedure. In one example, the electrodes can bechosen to make heat lesions at multiple levels of the spine or themedial branches of the spinal segmental nerves. In step 900, theelectrodes can be connected by cables to the high frequency generator.In step 904, the electrodes are positioned in the patient's body so thattheir tips are at the desired target tissue sites. Step 904 can, forexample, include the steps of stimulation-testing using the motor and/orphysiological stimulation signal output levels and pulse frequenciesthat can be user-selected from the system, applied at each electrodeindividually. In this way, the appropriate positioning of the individualelectrode tips can be confirmed at the correct position with respect tothe target nerves. In step 907, the desired set temperature can beselected on the interface of the high frequency generator. In oneexample, the set temperature can be the same for all of the electrodes,and, in another example, the set temperature can be different for theelectrodes, this chose be made by the clinician according to hisclinical needs. In step 911, the clinician can select the number ofmultiple electrodes that he desires to activate for the clinicalprocedure. The activation of the system can initiate a sequential and/orcyclical delivery of the high frequency signal output from the system tothe multiple electrodes in such a way that the signal output is appliedin a non-simultaneous time sequence. This can proceed by automaticallydelivering the high frequency output to one electrode at a timecorresponding to that electrode's programmed time slice, and accordingto a controlled sequence of time slices for the multiple electrodes, ashas been illustrated in the FIGS. 1 through 13. Step 911 can involvevarying the dwell time and/or the amplitude of the high frequency outputto each electrode during its time slice to maintain set a parametervalue, such as set temperature, as described in FIGS. 1-13.

The system and method described herein can be used in a variety ofmedical applications. In one example, it can be used to treat neuraltissue in the brain, spine, or peripheral anatomy to manage pain, mooddisorders, or movement disorders such as Parkinson's disease. In anotherexample, it can be used to treat cancerous tumors anywhere in thepatient's body. It can be to treat many various target tissue sites anddisease states, as can be considered by clinicians and others skilled inthe medical art.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingsClaims:

1. An apparatus for performing tissue modification procedures on apatient's body, comprising: a device connected to at least twoelectrodes, wherein temperature sensors are incorporated into tipportions of said electrodes; a high frequency generator operativelyassociated with said device, wherein said generator is configured todeliver non-simultaneously a high frequency signal output to each ofsaid electrodes in a cyclical sequence so that no two electrodes havesaid high-frequency signal output applied to them at the same time; anda feedback control circuit configured to regulate the signal outputdelivery to each of said electrodes so as to maintain a user settabletemperature at a tip portion of said electrodes when the electrodes arein contact with the patient's body based on temperature measurementsfrom said temperature sensors. 2-10. (canceled)